Filled float



Nov. 19, 1946.

Filed April 12, 1944 Patented Nov. 19, 1946 UNITED STATES PATENT OFFICE FILLED FLOAT Henry A. Gardner, Chevy Chase, Md.

Application April 12, 1944, Serial No. 530,704

6 Claims.

This invention relates to buoyant elements generally styled floats, which latter term is intended to include floats per se, buoyant compartments of ships and boats generally, weightsupporting buoyant elements of airplanes, and the like. The invention is particularly concerned with the provision of floats containing a light-weight water-resistant filling of such character as to delay the sinking of the floats, after puncturin of the same, for a protracted period. The invention is concerned not only with the provision of such filled floats but also with the filling compositions therefor and with methods of forming such fillings in situ within floats.

In my application Serial No. 530,703, executed November 30, 1943, now Patent No. 2,395,266, there is described a float containing a filling of a light-weight substance in comminuted form,

the particles of which substance repel water the filled float being capable of floating, after having been punctured, by reason of the waterrepelling action of the comminuted filling material. The examples of filling material included aluminum stearate powder, finely divided ma nesium stearate and lampblack. The presence of the fillin material at the opening caused by a puncture of the float shell repels the entrance of water through such Opening and makes possible the continued functioning of the float.

That method of filling a float element I call the "cold method.

It has now been found that the general objects of that inventive concept can be realized by filling the normally hollow space within the shell of the float element with a unitary, rigid, lightweight water-repelling filling body produced in situ within the float, said filling body having an apparent density less than that of water. This method is what I call the hot method, in which the filling body is formed in situ within the shell by the aid of heat.

This desirable result can be brought about by enclosing a relatively small amount of a mixture of suitable reactants within the float shell and effecting a reaction between said reactants through the agency of heat applied, whereby a suitable sponge or froth of reaction product filling, or substantially filling, said space is produced and thereafter solidified in spongy form. Preferably, the reactants mixture includes a metal powder and a resinous material having an acidic compound (or, the ingredients for a synthetic resin having an acidic component), which materials are capable of reactingin situ with evolution of vapor or gas. Desirably, there is inserted into the float shell an amount by volume of the reactants mixture which roughly corresponds to form one-eighth to one-fourth the volume of the shell, the float shell is then loosely covered, and thereafter the reaction is so effected that this volume of material, in the course of the reaction, puffs up to fill the space and solidifies, upon cessation of heating, to a rigid solid froth or honeycomb filling having a desirably low apparent density.

The resulting float filling has properties which, for some purposes, make it more desirable than the hereinbefore described float filled with water-repelling comminuted material. Thus, the float filling of the present invention is a unitary body which has no tendency to flow out of the float when the latter becomes punctured and is submitted to pressure. Again, because the filling is a unitary body of remarkable rigidity, hardness and toughness for all of its very. low apparent density, the float shell may be formed from a very thin skin of sheet metal (e. g., only strong enough to form an enclosure of definite volume for the reactants while the latter are being reacted, in situ, within it) which, alone, would be much too fragile for utility in a conventional float but which is desirably strengthened by the filling. In my preferred form of float construction, the main function of the shell is, or may be, that of providing a definite reaction space Within which to form a light-weight filling of predetermined porosity and apparent density; hence, it is not necessary that said shell be metallic provided it be impermeable and of sulficient strength to contain the reactants during the reaction. Plastic shells, for instance, may be employed. 1

The following specific examples are illustrative embodiments of the invention:

Example 1 A reactants mixture was formed by mingling 20 parts by weight of finely divided aluminum powder with 20 parts by weight of dry shellac, taken up in 80 parts by weight of alcohol.

The float shell used was a generally cylindrical vessel formed from thin sheet metal and having, when closed, a capacity of one gallon. One quart of the above reactants mixture was placed within the vessel. The opening was loosely covered and the. vessel'was heated at relatively low temperature, alcohol vapors being evolved. Thereafter, the vessel and contents were heated at about 170-480 C. for some (10 to 30) minutes. Under these conditions the shellac-aluminum powder mixture strongly puffed up, filling the entire space within the closed vessel with a honeycomb mass. When the vessel and contents were cooled, the foamy filling solidified to a rigid, solid sponge or froth having a brightly metallic appearance and an apparent density much lower than that of water. The so-filled float had desirable buoyancy, being capable of supporting a considerable weight.

The finished float was thereafter punctured in several places, and tested for buoyancy in punctured condition. It was found that the damaged float still maintained a satisfactory weight-supporting buoyancy, showing that a float so filled was useful for marine work even after having been punctured (e. g., by bullets.)

In'repetitions of the above-recited example the reactants mixture was heated at a variety of re-- action-inducing temperatures. It was found that the pulling reaction takes place, although much more slowly, upon ovening at temperatures as low as 60 C. However, the physical character of the product produced under the more energetic reaction conditions obtaining when the vessel and contents are heated at 170- 180 C. is much preferable to that of the prod- -uct formed at the very low reaction temperature mentioned.

In a modification of the above-recited specific example, there was added to the alcohol a very small amount (e. g., about 1% by weight) of caustic alkali. It was found that presence of the caustic alkali greatly accelerates the puffing reaction, causing the latter to be rather violent.

It has been found that essentially the same results are obtained when other acidic resins e. g., xanthorrhoea resin, resin, or an acidic synthetic resin of the polyhydric alcohol-polybasic acid typeare employed instead of shellac, and when other finely divided metals are substituted for the aluminum powder of the above-recited specific reactants mixture. Thus, powders of magnesium and of zinc have been tried with success. However, as willbe obvious, use of powdered. metals of low specific gravity (magnesium or aluminum) result in final products having particularly desirable properties from the standpoint of low apparent density.

Among the resinuous materials which have been found to be operable in carrying out the present invention are: shellac,.xanthorrho-ea resin, or similar heat-reactive resin, in the presence of any natural or synthetic resins such as phenolic resins, alkyds', maleic resins, vinyl resins, acrylic resins, urea-formaldehyde resins, cumarone indene resins, or such natural resins as the copals. When urea-formaldehyde resins areemployed, extremely rapid reactions occur, and when maleic resins are-employed numerous addition reactions of an important nature doubtless occur.

Example 2 A reactants mixture was formed by mingling 100 parts by weight of'maleic acid with 62 parts by weight of glycerin.

One pint (liquid measure) of this mixture was placed in a sheet metal vessel of one gallon capacity. The vessel and contents. were heated for some time at 230 C. At that temperature a reaction between the maleic acid and the glycerin occurred with formation of much gas, and the resulting resinous reaction mixture frothed and pufied up until-it substantially filled the closed vessel. When cooled, the frothy reaction mixture solidified into a rigid, solid sponge or froth of considerable porosity, having an extremely low apparent density.

The so-filled float had desirably good weightsupporting buoyancy, which property was not lost when the float shell was punctured.

In each of the experiments described in Examples land 2 above, the metallic froth filling produced in situ within the metal-walled container so tenaciously adhered to the latter that the filling and container could not be parted without disintegrating the one or the other.

In general repetitions of the example just described other polybasic acids than maleic acid, e; g., phthalic acid, have been found to be operable: also, mixtures of two or more polybasic acids (e. g., a mixture of phthalic and maleic acids) with polyhydric alcohol have been employed with success. Moreover, various combinations of synthetic resins (or' their components), natural acidic" resins and metal powders, and of synthetic acidic resins and metal powders, have been foundto be operable. Illustrative of such combinations is the following:

Emample 3 parts by weight of phthalic acid anhydride were reacted with 40 parts by weight of glycerin, and the temperature of the mixture was raised to about 225 C. to eliminate water and to produce a clear resinous substance. Into the partial reaction mixture; while ,still liquid, there were stirred 100 parts by weight of dry shellac and 40 parts by weight of aluminum powder. One pint of this mixture was placed in 'a' vessel of one gallon capacity, the cover of the vessel was loosely secured, and the vessel and contents were heated for some time (e. g., 20 minutes) at a temperature of approximately C., une der which conditions the reaction mixture was greatly puffed, by the evolvedgas, so that the reaction mixture substantially filled the space within the closed vessel. Upon cooling, the foamy reaction mixture solidified to a solid, porous body resembling a metallic sponge in appearance and having desirable rigidity, hardness, toughness and low apparent density.

In general repetitions of the above example I have formed the float-filling, in situ, from a mixture of equal parts by weight of xanthorrhoea resin and partially formed maleic "acid-glycerinresinwith aluminum powder, the weight ratio of aluminum powder to resin mixture being as 1 is to from 5 to 10 or more.

The heating required to raise the contents of the float element to pufiing reaction temperature may be effected in any suitable manner; the precise means employed is not critical. Thus; I- have found that the floats and their contents'can be heated to the desired temperature in suitable ovens, or in oil baths or other baths of high boiling liquid heated to the desired temperature, or with internally applied electric resistance apiparatus or other known method of heating:

' It should be understood that I can produce my 'solid filling body without the use of metallic powders. While the lat er are not necessary, it is a fact that the metallic powder combinations often. are desirable because of their greater strength.

One embodiment of the filled float element of the present invention is illustrated in the accompanying drawing, in which Fig. 1 is a view of a conventional float, with aand Fig. 2- is a greatly enlarged fragmentary sectional view illustrating schematically the nature of the filling body.

According to the drawing, the filling body A is a unitary, rigid, solid froth structure filling the interior space of the thin-Walled spherical float shell B. As shown, a plurality of attachment eyes C are provided about the spherical shell. A relatively small (e. g., 2-inch) opening D in the shell B likewise is provided, the opening normally being closed by screw cap closure E. The drawing (Fig. 2) illustrates the filling material produced according to Example 3 above.

I claim:

1. A buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of a resinous material containing an acidic component with a powdered light metal reactive therewith, said metallic sponge filling a normally impermeable and rigid closed casing member.

2. A buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of an acidic resin with powdered aluminum, said metallic sponge filling, and tenaciously adhering to a normally impermeable and rigid closed metal casing member.

3. A-buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of an acidic resin with powdered aluminum, said metallic sponge filling, and tenaciously adhering to a normally impermeable and'rigid closed metal casing mem her.

4. A buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of an acidic natural resin with powdered aluminum, said metallic sponge filling, and tenaciously adhering to a normally impermeable and rigid closed metal casing member.

5. A buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of shellac with powdered aluminum, said metallic sponge filling, and tenaciously adhering to a normally impermeable and rigid closed metal casing member.

6. A buoyant element comprising a rigid solid porous metallic sponge, having an apparent density substantially less than that of water, composed of a reaction product of an acidic alkyd resin With powdered aluminum, said metallic sponge filling, and tenaciously adhering to a normally impermeable and rigid closed metal casing member.

HENRY A. GARDNER. 

